Hearing aid receivers or loudspeakers have conventionally been mounted in both BTE (behind the ear) and ITE (in the ear) hearing aids with the use of resilient suspensions to suppress or attenuate mechanical vibrations of the receivers and prevent that these were transmitted to a microphone of the hearing aid. Due to the requirements of very large acoustical gain between proximately located microphone and receiver components, the utilization of the resilient suspension has been required to avoid feedback oscillation caused by coupling of mechanical vibrations between the receiver and microphone.
Conventional or prior art resilient suspensions include elastomeric rubber boots and elastomeric strips or ribbons mounted to partly or fully encircle the receiver housing and optionally were provided with shock absorbing protrusions and several other types of resilient supports. Through careful design of the resilient properties of these prior art resilient suspensions these have been adapted to attenuate or decouple mechanical vibrations of the receiver so as to prevent these from being coupled to the housings of the BTE and ITE hearing aids.
Furthermore, electrical signals from a hearing aid amplifier to the receiver have conventionally been provided through, for example, a pair of flexible electrical leads such as multi-core litze wires soldered to respective terminals of the receiver.
These prior art hearing aid constructions incurred a number of technical problems that are overcome by the present inventions.
One problem associated with the above-mentioned hearing aid construction techniques is the space requirement inside the hearing aid shell to accommodate the resilient suspension and flexible leads. In small hearing aids such as the ITE type of hearing aids and in particular in ITC (in the canal) and CIC (completely in-the-canal) type of hearing aids, the available space for the resilient suspension at a tip of the hearing aid shell is typically very limited since the shell tip must be dimensioned for placement deeply inside the ear canal of the user or patient. Another problem is that even if adequate space for the resilient suspension is available at the tip of the hearing aid shell, the correct placement of the resilient suspension can be very difficult and therefore time consuming for the assembly technician because it must be ensured that the resiliently suspended receiver is allowed substantially unrestricted vibration does not contact the walls of the hearing aid shell. Finally, the correct placement of the resiliently suspended receiver is subjected to additional difficulties by the presence of the pair of flexible electrical leads which tends to pull or push the receiver away from the correct position due to the stiffness of the leads and the low weight and resilient suspension of the receiver.
These problems are firstly encountered during manufacture of the hearing aid but, unfortunately, resurface if the hearing aid receiver malfunctions or fails in the field and needs replacement in a service and repair shop. This is, unfortunately, a very common situation because the receiver is placed at a very exposed position deeply inside in the user's ear canal where it is subjected to moisture and cerumen contamination. In this latter repair situation, it may be an even more difficult task for the service technician to ensure correct positioning of the replacement receiver inside its resilient suspension and the shell part(s) because he may lack adequate instructions, measurement equipment or training to complete the task. Furthermore, in prior art ITE hearing aids, the receiver has only been replaceable from a rear portion or so-called faceplate portion of the aid where a substantially plane pre-manufactured plastic plate has been glued to the upper circumferential portion of the hearing aid shell so as to isolate the interior of the hearing aid from the surrounding environment. Accordingly, to replace the defective receiver, the faceplate portion of the aid had to be re-opened with a substantial risk of damaging the customized ITE shell and/or mechanical or electronic components housed within the shell.
U.S. Pat. No. 4,109,116 discloses a miniature dual-diaphragm moving armature receiver for hearing aid applications. The dual-diaphragm receiver is formed as a back-to-back mounted assembly of a pair of conventional single diaphragm moving armature receiver to achieve cancellation of mechanical vibrations of the receiver. The dual-diaphragm receiver is mounted inside an earphone and the earphone may be inserted into and acoustically coupled to an earmold that is insertable in the ear canal of a hearing aid user. The disclosed dual-diaphragm moving armature receiver does not comprise a common front chamber or a common back chamber but has separate chambers coupled exclusively to each single diaphragm receiver.
WO 2004/049756 discloses a single diaphragm moving armature receiver that comprises a motion reversing arrangement or linkage assembly coupled between a diaphragm and the moving armature. If the effective moving masses of the armature assembly and the diaphragm assembly are made identical, some cancellation of mechanical vibrations of the receiver can be achieved.
US 2003/0048920 describes a receiver having two sound outputs for different frequency intervals. These outputs are derived from the front and back chamber, respectively, of the receiver and output from different outputs of a housing.